targets, man-made infrastructures, such as dams, buildings and airports. The fast delivery of Sentinel data to the public made it
possible to do real time monitoring and publish useful information at first time. A number of projects already
demonstrated the potential of S-1A interferometry, including for instance application to volcano monitoring González et al.,
2015 or observation of effects of the earthquake in Chile Grandin et al., 2016, South Napa Polcari et al., 2014 or
Pishan in China Wen et al., 2016.
2. INHABITED SLOPES
The strategy of applying common multitemporal InSAR techniques such as PermanentPersistent Scatterers PS InSAR
yields in very reliable results and possibility to obtain dynamics of the movement within estimated data time series.
However the reliability depends on the presence of temporally coherent scatterers, such as buildings or at least bare rocks. The
high revisit time of S-1A allows frequent measurements that captures PS dynamics in a higher temporal detail than using
e.g. Envisat ASAR system and thus may evaluate also movements with a higher velocity rate.
2.1 Babadag, Turkey
Babadag is a small town of Turkey and 30 km away from the centre of the city Denizli in Aegean region Lat:
37°4838.37N, Lon: 28°5133.38E which has been seriously affected by a landslide phenomena since last 60 years. The
Babadag landslide has been evaluated from Envisat in a previous work Lazecký et al., 2015. Because of low number
of images and high rate of decorrelation in the area also due to fast movements, the result could be achieved only using an
MT-InSAR methodology using only coherent spatially filtered interferograms rather than the whole time series in the PS
algorithm. In this case, Quasi-PS technique was used Perissin et al., 2007. In case of processing based on S-1A, a higher rate
of deformation could be captured reliably due to a higher revisit time. With only 12 images used from 10
th
September 2015 – 20
th
March 2016, the PS processing allowed detection of movement in the rate of almost 100 mmyear in the satellite
line-of-sight LOS. The result is shown in Fig. 1. The technology reveals a continuous movement of the slope in a
relatively high rate. Babadag village has been evacuated already in 2006 Canaslan-Comut et al., 2015a.
Figure 1. A high rate of landslide movement detected by Sentinel-1A PS InSAR over Babadag village, Turkey.
2.2 Prievidza, Slovakia
The region of Prievidza, in the central part of Slovakia, is affected by various types of slope failures, especially
landslides. The 2012-2013 reactivation of slope deformations in Hradec and Velka Lehotka suburbs of the Prievidza city
Slovakia caused serious damage to the local infrastructure and buildings. The assessment of the physical activity in these
locations of active landslides becomes crucial after attaining emergency conditions in June 2013. Current monitoring
techniques were focused in observation of the groundwater level and precise inclinometer measurements. While the method
of precise inclinometer provides information on the deformation evolution directly on the shear zone over the
points within surroundings of monitored objects, the InSAR observations enable to assess the deformation phenomena fully
across the sliding areas.
In the area of 4.5 x 4 km 18 km
2
391 and 425 radar scattering targets have been identified in ascending and descending track,
respectively. The multivariate outlier removal procedure Bakon et al., 2016 have been applied in order to preserve
spatial and statistical dependency among low coherent observations, preserving 122 and 39 targets that would be
discarded by the standard thresholding with 0.7 on ensemble coherence value. The deformation maps Fig. 2 are the result
of PS InSAR analysis of 52 S-1A images acquired over ascending 175 29 and descending track 175 23 in the period
from 102014 to 112015. Both ascending and descending velocities were referenced to the same reference point located
in the most stable northern part of the Hradec village, that rest exclusively upon the jointing edges of the landslide, on the
block formed by lava flows of pyroxene andesites.
Figure 2. Deformation maps with mean LOS velocities obtained by PS InSAR analysis of Sentinel-1 radar imagery from
ascending and descending track. Thanks to availability of both sensing geometries, a
decomposition to vertical and one horizontal component in descending azimuth look direction is possible. The strategy for
3D decomposition holds for: i subdivision of the area into the regular grid of 50 x 50 m; ii obtaining geographical
coordinates for the centres of each grid cell; iii computing mean LOS velocities for the cell centres using all the scatterers
allocated within the same cell and separately for ascending and descending track; iv computing vertical and horizontal
displacement velocities Fig. 3 based on Samieie-Esfahany et al., 2009.
Figure 3. Horizontal descending azimuth look direction and vertical up and down direction displacement velocities in
centres of the regular grid 50 x 50 m. The areas affected by strong deformation process are evident
over vast majority of Hradec and Velka Lehotka suburbs Fig. 1, 3. The active parts of the area are corresponding mainly to
the landslide deluvia and they are in agreement with boundaries of active landslides that were geologically mapped by Malgot
et al., 1983. Since the deformation process detected in ascending track towards the satellite occurs in opposite
This contribution has been peer-reviewed. doi:10.5194isprsarchives-XLI-B7-775-2016
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direction in comparison to descending track away from the satellite, the real movement vector of the monitored area
appears to have significant transition in horizontal direction. It is necessarily to be noted that while exploiting former ERS
and ENVISAT missions, this deformation processes remained unnoticed due to rapid changes that were undetectable utilising
revisit periods of 35 days and more. Since the deformation phenomena is persistent over recent days and the area is under
vital monitoring efforts, this underlines the operational capability of S-1A observations for routine updates of active
landslide maps.
3. NATURAL SLOPES
